The owner of said land may apply for a special permit from the Planning Board for the issuance of more than seven building permits in any twelve-month period. The Planning Board may grant a special permit only if the Board determines that the probable benefits to the community outweigh the probable adverse effects resulting from granting such permit, considering the impact on schools, other public facilities, traffic and pedestrian travel, recreational facilities, open spaces and agricultural resources, traffic hazards, preservation of unique natural features, planned rate of development, and housing for senior citizens and people of low or moderate income, as well as conformance with Master Plan or Growth Management Plans prepared by the Planning Board pursuant to MGL c. 41, § 81D. The Planning Board shall give particular consideration to proposals that demonstrate a reduction in allowable density of 50% or more.